Circuit breaker with mechanically isolated trip mechanism



April 20, 1965 P, KOVAL ETAL 3,179,768

CIRCUIT BREAKER wITH MECHANIGALLY IsoLATED TRIP MECHANISM Filed May 3,' 1962 2 Sheets-Sheet 1 /NvE/vToRs: LEON/0E P. KovAz., MAUR/c5 E S/Ro/s,

By @M7-'C ATTORNEY.

April 20, 1965 P. KovAL ETAL 3,179,768

CIRCUIT BREAKER WITH MECHANICALLY ISOL Filed May :5, 1962 ATED TRIP MECHANISM 2 Sheets-Sheet 2 l-w'm /NvE/vroRs: LEON/DE R KovAL, MA uR/CE f. S/Ro/s,

ATTORNEY.

UnitedStates Patent The present in ention relates t-o electric circuit breakers, and particularly to electric circuit breakers of the type comprising a main molded insulating enclosure or case containing relatively fixed and movable contacts and manually operable operating mechanism therefor, includinga releasable member for causing automatic opening of the contacts, and avseparately enclosed current- `responsive mechanism or trip unit contained within the main enclosure'or case and adapted tocause release of the releasable member/and automatic opening of the contacts upon the occurrence of predetermined current conditions through the circuit breaker.

Such separately enclosed current-responsive mechanisms or trip units are commonly adjusted or calibrated to cause Vautomatic opening of the circuit breaker upon the occurrence of particular predetermined currentconditions, before the trip unit is mounted in the main case 'of the circuit breaker. This not only facilitates the necessary ladjustments to the trip unit, but permits the changing of trip unitsby the user.

Commercially usable circuit breakers and trip units heretofore available have suffered from'the disadvantage that when a pre-adjusted or calibrated trip unit is mounted in a circuit breaker, it is sometimes found that the trip unit does not operate within the preset range 0f current conditions.'y This has been discovered to be due V`two two main factors: (1)the fact-that the contact operatoperating mechanism is altered thereby.

.It isan object of the present invention .to provide an electric circuit breaker of the type referred to comprising a pre-calibratable trip unit Whose adjustment or point of operation Vis not altered by minor variations in mounting of the tripunit inthe main casing or by minor variations in the force tending to operate the rele-asable means of the contact operating mechanism.

jIt is another object of the invention to provide a trip unit of the type described the setting or calibration of which is unatiected by variations in mounting or operating mechanism force and which requires no corresponding special modification o f the circuit breaker operating mechanism.k

It is a further object of the invention to provide a precalibratable trip unit of the type described which requires the use of a minimum number of parts.

In accordance with the invention, a circuit breaker is providedcomprising amain casing including relatively fixed and movable contacts Iand manually operable operating mechanism therefor including a first member *releasableto cause automatic opening of the contacts, and

a separately'enclosed trip unit mounted in the main casing and vincluding a first restraining means for releasably restraining the first releasable member. Means is also provided in the trip unit for moving said first restraining means, comprising a second releasable member, biased ICC to cause movement of the first 'restraining means, and releasably held against such movement. The trip unit of the present invention further includes means for causing release of the second releasable member in response to predetermined current conditions.

Further, in accordance with the invention, the force exertedk by the second releasable means within the trip unit is made appreciably greater than the force normally required to move the said first restraining means. The excess of the force exerted by the second releasable means over that normally required to move the first restraining means is such that ordinarily encountered variations in the force required to move the said first restraining means have no effect on the operation of the trip unit.

The invention will be more fully understood from the following detailed description, and its s-cope will be pointed out in .the appended claims.

In the drawings, v

FIGURE l is a side elevation view of an electric circuit breaker incorporating the invention, a portion of the side Wall of the maincasing being broken away;

FIGURE 2 is an end elevation view of the trip unit of the circuit breaker of FIGURE 1, taken on the line 2-,2 of FIGURE 1;

FIGURE 3 isa sectional view of the trip unit of the circuit breaker of FIGURE 1, taken substantially yon the line 3--3 of `FIGURE 2;

FIGURE '4 is aview of a portion of the mechanism of the trip unit as shown in FIGURE 3, shown in releasing position; and

FIGURE 5 is a perspective view ofthe latching mechanisml of the tripunit of FIGURES 1-4.

' Referring first to FIGURE l, the invention is shown as incorporated in a circuit breaker comprising a mainV molded insulating enclosure -or casev 1f), containing three incoming and three outgoing terminal means 11 and 12 respectively, only one of keach shown.

A pair of relatively movable contacts 13, 14is provided connected between each terminal 11 and a corresponding terminal 12. The contact'13 is rigidly mounted on the Aterminal conductorill, whilethe contact`14 is mounted on a contact support 15 pivotally supported at 16 on a movable contact arm 17, and a compression spring A15A is `provided'therebetween` The contact arm 17 i i turn, is rigidly supported on acontact Cross-arm 18, pivotally supported at its ends on suitable bearings, not shown. mounted in the -base of the casing `10.

, It will be'understood 'that the cross-arm 18 extends across all three poles of the circuit'breaker, and carries three contact arms 17, although only one, the central of the three, is shown in FIGURE 1.

'.Eaoh contact support 15 Vis Iconnected by a vflexible con- 4ductoror braidz19 to a correspondingterminal strap 20 A releasable member 25 is valso pivotally supported on a fixed pivot pin V26 carried by the supporting frame.

A pair of toggle-links 27, 28 are connected between the releasable member 25 and the contact arm 17, at pivots 29 and 30 respectively, and are interconnected by a knee pivot pin31. l i A tension spring 32 is connected between the handle- 3 support member 23 and the knee pivot pin 31 of the toggle linkage.

In operation, the handle 22 is 'oscillated about its pivot 24 from the ON position shown in FIGURE 1 to the left as viewed to an OFF position, moving the tension spring 32 across the line of centers of the pins 31 and 29, moving the toggle linkage 27, 2S, to a collapsed condition, 'and moving the contact arm 17 upwardly to an OFF position. l The releasable member 25 has a latch portion 25A, see FIGURES 3 and 4, which is releasably held by a latch carried by the trip unit 21 in a manner to be described. When the operating mechanism is in the ON condil'tion as shown in FIGURE 1, release of the releasable member 25 permits this part to move clockwise about its pivot 26 under the influence of the tension spring 32, moving the contact arm 17 upwardly to OFF position and causing collapse or partial collapse of the toggle linkage 27, 28.

Subsequent resetting of the member 25 is accomplished by manually moving the handle 22 to OFF position, causing an extension 23A of the handle support member to engage the member 25 and rotate it counterclockwise `to relatched position.

Trip unit 'the case 35 by means of screws 37. Each incoming terminal strap 2t) is xedly attached to the case 35 by means of screws 38.

The trip unit as a whole is xedly mounted in the case by means of screws 39 which serve to attach the flexible conductors 19 to the straps 20 and also pass through the straps and threadedly engage tapped inserts 40 in the base of the case 10.

The strap 12 is connected to the strap 20 by a conductor 42, which makes a complete turn about a trst magnetic core 43, extending between two generally planar magnetic side plates 44, only one shown.

A second magnetic core 45 is also supported between the side plates 44. Mounted on the core 45 in insulated relation, is a loop or ring 46 of highly conductive material such as copper.

A thermally-responsive member, comprising an elongated bimetallic strip 47, is rigidly affixed to the loop 46 by suitable means, such as by welding.

In operation, current passing from the strap 12 to the strap 20, through the conductor 42 causes that conductor to act as the primary of a transformer, setting up magnetic llux through the magnetic path comprising the core 43, side plates 44, and core 45. This causes a secondary current to be induced in loop 46, generating heat therein. The heat generated in loop 46 is transferred by conduction to the bimetallic strip 47, which is so constructed and arranged as to deflect to the right as viewed, moving the adjusting screw 48 to the right to cause tripping or release of the releasable means in a manner to be described.

It will be understood that as previously mentioned, three outgoing terminal straps 12 and incoming straps 20 are provided, each having associated therewith, parts as illustrated in FIGURE 3 including conductors 42, magnetic systems including cores 43, side plates 44, and cores 45, as well as conductive loops 46 Iand bimetallic strips 47 with adjusting screws 48.

Latchng mechanism In accordance with the invention, latching means is provided including a common trip bar 50 of molded 1nsulating material, extending across all three poles of the 4 circuit breaker trip unit, and adapted to be rotated about its pivot 51, by the bimetallic strips 47.

The common trip bar 50 is also adapted to be rotated about its pivot 51 by magnetic action. For this purpose, the side plates 44 are provided with pole extensions 44A. A magnetic armature 52 is also provided at each pole, pivotally supported, independently of the trip bar 50, on the pivot pin 51. Each armature 52 has an extension 52A having a portion adapted to engage a portion of the trip bar 5t) to rotate it clockwise when the armature 52 is attracted to the pole extensions 44A.

The molded insulating trip bar S0 includes a centrallylocated extension 50A, having a rounded end portion 50A disposed to engage an arm 53, see FIGURE 5 of the latching mechanism which will now be described.

Referring particularly to FIGURES 3-5, the latching mechanism of the invention comprises a supporting frame 54, se'e FIGURE 5, comprising two opposed side portions 55, 56, joined by a bight portion 57, and supported within an aperture 36A, see FIGURE 2, in the cover 36. The side portions 55, 56 each include an outwardly-directed tang 71, 71 respectively, having holes 72, 72', by which the frame 54 is adapted to be rigidly attached to the cover 36 of the trip unit housing by suitable means such as by screws, not shown.

For the purpose of releasably restraining the primary releasable member 25, the latching mechanism includes a primary latch member 58 pivotally supported between the sides 55, 56 on pivotal supports 59. T-he primary latch member 58 includes a latching portion 58A adapted to engage the latch portion 25A of the releasable member 25.

For the purpose of causing releasing movement of the primary latch member 58 upon the occurrence of predetermined current conditions, a tripping or kick-off member 60 is provided, pivotally supported on a pivot pin 61, extending between the sides plates 55, 56.

The tripping or kick-olf member 60 includes an extension 60A having a notch 60B, providing a secondary latch surface.

In the normal condition of the parts, as shown in FIGURE 3, the kick-off member 60 is releasably restrained from counter-clockwise movement by engagement of `an arm 62 of a secondary latch member 63.

The secondary latch member 63 is pivotally supported on pivot pin 64 extending between the sides 55, 56 of the frame 54. The secondary latch member 63 is generally U-shaped, having a bight portion extending generally parallel to the pin 64, a latch arm 62, and an actuating .arm 53.

The secondary latch 63 is biased clockwise about its pivot pin 64 by the action of one end portion 65 of a coil spring 66, acting on a pin 67 carried by the arm 53. The other end, 68, of the spring 66 engages the primary latch member 58, and biases it in a clockwise direction.

The primary latch member 58 includes a downwardly directed extension 58B, see FIGURE 3, which engages the pin 61 to limit movement of the member 58 in counterclockwise direction as viewed in FIGURE 3.

The secondary latch member 63, at its arm 62, engages a wall of the notch 60B of the arm 60A of the kick-off member 60 as a stop to limit movement of the member 60 in counterclockwise direction. It will be observed that this provides a fixed accurately controllable amount of latch overlap of the secondary latch arm 62 and the tripping member 60.

For the purpose of biasing the kick-off member 60 in counter-clockwise direction as viewed in FIGURE 3, a kick-off spring 70 is provided, carried by the pin 61. One end 70A of the spring 70 is normally in engagement with the casing cover 36, while the other end 70B, is in engagement with an edge portion of the member 60.

For the purpose of engaging and moving the primary latch member 58, the kick-oli member 60, at its right side as viewed in FIGURE 5, includes two actuatingr projections. The first suchproje'ction is designated as 60C, see FIGURE'4, and the secondl such projection is designated as 60D, also in FIGURE 4;

It willbe observed by reference to FIGURE 3, that projection 60C is normally substantially in engagement with thel extension 58B of the primary latch. 58. The projection 60D, of the kick-olf member 60 is normally spaced a shortdistance from a corresponding surface 58C of the member 58.

It will be observed that the latching system just described comprises a primary latch `member SS, restraining the-y releasable member 25, and asecondary latch member63; restraining the kick-ott member d0. All ofthe aforesaid members are preferably mounted on the cover member 36 of the trip unit 421. This permits these parts to be readily assembled before the cover member ismourited on the enclosure body 35.

Itwill be observed, moreover, that in the normal condition ofthe parts as indicated inFIGURE 3, these latch systems are independentof each-other. Inother Words, the primary latch is biased against the pin 61 as a stop, andl is unaffectedby'movement ofthe secondary latch 63 until the kick-olf member. 60 Vis released.

In operation, therefore, the occurrence of predetermined abnormal current conditions in the circuit including terminal straps 12j and 20 and conductor 42 causes rotation of the common trip bar 50. This may occur by reason ofthe heating and deection of the bimetallic strip 4'7 as'on gradual overload currents, or by reason of the attraction of the armature 52 to the pole extensions 44A as onthe sudden high short-circuit currents.`

Rotation of the trip bar StD-causes engagement of the projection 50A of the trip bar 50'with the arm 53 of secondary latch 65. Rotation of the secondary latch 63 a predetermined amount causes release of the kick-olf member 60.

Upon release, the member 60 is moved by spring 70 in a counter-clockwise direction. Y

`During the initial portion of its movement, Vthe projection 60A of the member llvengages the extension 58B of the member 58, providing a pry-olip action to overcome static friction of the latch 58A of the member 58 and the latched portion 25A of the member 2S.

Subsequent movement of the member 60 causes the projection 60D to engage the edge surface 58C of the member 58 to, move it to fully released position, releasing the member 25 to cause opening of the contacts of the breaker.

Following Vrelease of the releasable member 2S, the parts may -be reset to permit subsequent reclosing of the contacts. YSuch resetting, is accomplished by moving the handle 22 counterclockwise, causing projection `23A of theV handle-support member 23 to engage the releasable member 25 ,and rotate it also in counter-clockwise direction. l

Referring toFIGURE 4, when the member 25 is thus rotated counter-clockwise,` itmoves downwardly toward the. tripping member 60, and engages the edge portion 60E ofy thermember, rotating it clockwise to permit the arm, 62' of the secondary latch member to drop into the notch 60B. nThe jprirnary latch `58 is simultaneously moved to latching position against the pin 61 and engages theV tip 25A of the member 25 when it moves upwardly.

For the purpose of ensuring release of the primary latch member S upon release of the kickoff member 60, the kick-off spring 70 is made of such strength as to be capable of delivering a force substantially greater than that required to release the primary latch 58.

By this means, it is possible to calibrate or adjust the trip unit 21 apart from the main circuit breaker, with the assurance thatthe setting will not be disturbed although the force required to move the primary latch 58 may vary within certain pre-determinable extremes because of variations of the mounting of the trip unit 21 in the case l0,

or because of variations in the forcenecessar-yto restrain the releasable member 25.

It will be observed, also, that the critical isolation of the calibration of thetrip unit 21 is accomplished in accordance with the inventiomby the use of a single secondary latch member, which is acted upon by the common trip bar, which in turn isl actedrupon by the current responsive means (either` the bimetallic strips 47` or the magnetic armatures 52) of each poleA ofthe circuit breaker.

While only one embodiment of the invention hasbeen described, it will be appreciated that many modifications thereoffmay be made, and yit is intended, therefore, that the appended claims shall` coverv all such modifications as fall within the true spirit and scope ofthe invention.

We claim:

1. A multi-pole electric circuitl breaker comprising;

(a) a main insulating casing,

(b) at least two pairsof relatively movableV contacts supported in said casing,

(c) manually operable operating mechanism in said main casing for moving saidl contacts between open and closed circuit positionsk and including a member releasable to cause automatic opening of said contacts,

(d) a primary latch disposed and arranged to releasably engage said releasable memberI of said operating mechanism,

(e) a separately enclosed trip unit removably mounted in said main insulating casing, l

(f) a tripping member carried` by said trip unit, biasing means carried by said trip unitvr separate fromk said operating mechanism acting, on said tripping member and biasing said tripping member to exert a force on said primary latch,v

(g) a secondary latch carried by said trip unit ably restraining said tripping member,

(Iz) a common trip bar carried by said trip unit and extending across all poles of said multi-pole circuit breaker,

(i) at least one current-responsive means carried by said trip unit for each of said poles and disposed and arranged to engage said common trip vbar and,r

(j) said common trip bar includingV means forcausing release of said secondary latch upon a predetermined amount of movement of said common trip, bar by said current-responsive means,

(k) said tripping member when released acting on said primary latch to cause release of said releasable member.

2. A multi-pole electric circuit breaker comprising:

(a) a main insulating casing,`

(b) at least two pairs of relatively movable contacts supported in said casing,

(c) manually operable operating mechanism in said main casing for moving said contacts betweenv open and closed circuit positions and including a member kreleasable to cause automatic opening of said contacts,

(d) a separately enclosed trip unit removably mounted in said main insulating casing,

(e) a primary latch carried by saidl trip unit and disposed and arranged to releasably engage sad releasable member of said operating mechanism when said trip unit is mounted in said main casing,

(f) a trippingmember carriedby said trip unit, biasing means carried by said trip unit separate from said operating mechanism acting on said tripping member and biasing said tripping member to exert a force on said primary latch,

(g) a secondary latch carried by said trip unit releasably restraining said tripping member,

(h) a common trip -bar carried by said trip unit and extending across all poles of said multi-p0le circuit breaker,

releas- (i) at least one current-responsive means carried by said trip unit for each of said poles and disposed and arranged to engage said common trip bar and,

(j) said common trip bar including means for causing release of said secondary latch upon a predetermined amount of movement of said common trip bar by said current-responsive means (k) said tripping member when released acting on said primary latch to cause release of said releasable member.

3. A multi-pole circuit breaker as set forth in claim 2, said trip unit including a generally box-like insulating enclosure having an open side wall and a generally planar insulating cover member attached to said enclosure and closing said open side Wall, said primary latch, said tripping member and said secondary latch being carried by said cover member.

4. A multi-pole circuit breaker as set forth in claim 1 wherein said tripping member includes an integral stop portion which determines the amount of latch engagement of said secondary latch member with said tripping member.

5. A multi-pole circuit breaker as set forth in claim 1 wherein said current responsive means comprises an elongated bimetallic strip for each pole of said circuit breaker having means thereon for engaging said common trip bar, and wherein said current responsive means also comprises a magnetic armature for each pole of said circuit breaker, said armatures each being movable to cause releasing movement of said secondary latch independently of said bimetallic strips.

6. A multi-pole circuit breaker as set forth in claim 2, said tripping member having a rst portion thereof adapted to engage said primary latch member at a first point and a second portion thereof adapted to engage said primary latch at a second point, said first point of engagement being spaced farther from the pivot of said primary latch than said second point.

7. A multi-pole electric circuit breaker comprising:

(a) a main insulating casing,

(b) at least two pairs of relatively movable contacts supported in said casing,

(c) manually operable operating mechanism in said main casing for moving said contacts between open and closed circuit positions and including a member releasable to cause automatic opening of said contacts,

(d) a trip unit removably mounted in said main insulating casing and including a trip unit insulating casmg,

(e) a primary latch disposed and arranged to releasably engage said releasable member of said operating mechanism when said trip unit is mounted in said main casing,

(f) said trip unit having a tripping member, biasing means carried by said trip unit separate from said operating mechanism acting on said tripping member and biasing said tripping member to exert a force on said primary latch, said tripping member when released acting on said primary latch to cause release n of said releasable member,

(g) said trip unit having a secondary latch normally releasably restraining said tripping member,

(h) said trip unit having a common trip bar extend ing across all poles of said multi-pole circuit breaker,

-(i) at least one current responsive means carried by said trip unit for each of said poles and each disposed and arranged to engage said common trip bar,

(j) said common trip bar including means for causing relase of said secondary latch upon predetermined movement of said common trip bar by said current responsive means,

(k) said trip unit being mounted in said main casing with a predetermined wall portion of said trip unit casing adjacent said operating mechanism,

(l) a metallic frame member mounted on said predetermined Wall of said trip unit casing, said frame member having a pair of spaced apart side portions,

(m) said primary latch member and said tripping member both being carried by said metallic frame member between said opposed side portions,

(n) said lpredetermined wall of said trip unit casing having an opening therein,

(o) said frame member being supported on said wall adjacent said opening to permit said primary latch member to cause release of said releasable member of said operating mechanism and said common trip bar to cause releasing movement of said tripping member.

8. A multi-pole electric circuit breaker as set forth in claim 7 wherein said primary latch member cooperates with said relasable member outside of said trip unit casing and said tripping member cooperates with said secondary latch means inside said trip unit casing.

9. A multi-pole electric circuit breaker as set forth in claim 7 wherein (a) said main casing includes a bottom wall supporting at least one of each of said pairs of relatively movable contacts and said manually operable operating mechanism, said trip unit casing being mounted on said bottom wall, with said predetermined wall portion of said trip unit casing extending substantially perpendicular to said bottom Wall,

(b) said side portions of said bimetallic frame member also extending substantially perpendicular to said back wall,

(c) said primary latch member being pivotally supported between said side portions of said frame member,

(d) said tripping member being pivotally supported between said side portions of said frame member at a point substantially closer to said back wall than said primary latch member.

References Cited bythe Examiner UNITED STATES PATENTS 1,955,327 4/34 Dorfman 200-116 2,047,739 7/36 Lingal 200-88 2,047,816 7/36 Atwood 200-116 2,140,360 12/38 Jennings 200-88 2,401,005 5/46 Lindstrom 200-88 2,419,125 4/ 47 Dorfman et al. 20G-88 2,458,151 1/49 Dorfman et al 200-88 2,465,789 3/49 Butler 200-116 2,491,959 12/49 Dyer 200-88 2,673,908 3/54 Brumfield 200-88 2,686,242 8/54 Leonard et al 200--116 2,736,010 2/56 Ridgley 200-88 2,795,670 6/57 Cellerini 200-88 2,900,473 8/59 Giessner 200-88 2,908,782 10/59 Kiesel et al. 200-88 BERNARD A. GILHEANY, Primaly Examiner, 

1. A MULTI-POLE ELECTRIC CIRCUIT BREAKER COMPRISING: (A) A MAIN INSULATING CASING, (B) AT LEAST TWO PAIRS OF RELATIVELY MOVABLE CONTACTS SUPPORTED IN SAID CASING, (C) MANUALLY OPERABLE OPERATING MECHANISM IN SAID MAIN CASING FOR MOVING SAID CONTACTS BETWEEN OPEN AND CLOSED CIRCUIT POSITIONS AND INCLUDING A MEMBER RELEASABLE TO CAUSE AUTOMATIC OPENING OF SAID CONTACTS, (D) A PRIMARY LATCH DISPOSED AND ARRANGED TO RELEASABLY ENGAGE SAID RELEASABLE MEMBER OF SAID OPERATING MECHANISM, (E) A SEPARATELY ENCLOSED TRIP UNIT REMOVABLY MOUNTED IN SAID MAIN INSULATING CASING, (F) A TRIPPING MEMBER CARRIED BY SAID TRIP UNIT, BIASING MEANS CARRIED BY SAID TRIP UNIT SEPARATE FROM SAID OPERATING MECHANISM ACTING ON SAID TRIPPING MEMBER AND BIASING SAID TRIPPING MEMBER TO EXERT A FORCE ON SAID PRIMARY LATCH, 